Sump/Refugium setup and overflow/return questions

[Dmmuir]

Working on getting details together for assembly. My tank has 4 holes, 1 larger and 1 smaller in each back corner. I know the larger is the drain and smaller the returns.
How tall and what configuration should the PVC inside the tank be set?

Also, the sump, what should be in there at this point. right now it's empty, and I think it's set to be able to use as a refugium in the future also.

Tank is a 5' 120Gallon, anyone have pics/drawings/recommendations on piping drains and returns?

 

[Snoopy 67]

Herbie Drain is the way to go in each overflow.
https://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

 

[Dmmuir]

Herbie Drain is the way to go in each overflow.
https://gmacreef.com/herbie-overflow-reef-tank-plumbing-method-basics/

And then I would go over the side for a return? I'd have 1 siphon and 1 emergency in each weir?

 

[Snoopy 67]

Correct. Use the bigger hole as the emergency in each overflow box.
GATE VALVES on the siphon drains. Some fluctuation with levels inside the overflows is normal.
I use Sea Swirls on my tank coming back in over the top.
The link I listed tells you everything you need to know